Cryogenic technology provides cooling to very low temperatures. It is widely used in medicine, and particularly in surgery. Freezing tissue can kill its cells, and this makes cryosurgery particularly useful for treating cancerous growths. A cryogenic-probe may be used to kill the cells of malignant cysts in mammary tissue. The cryoprobe is required to have a small diameter to cause minimal damage and trauma to the body tissue in its passage through body tissue.
Typically, the site requiring treatment is significantly larger than the diameter of the cryoprobe and is all too frequently wider than the effectively frozen volume of tissue that is treatable by a single probe insertion. Use of multiple probes causes additional trauma and discomfort. Indeed, it will be appreciated that resorting to such procedures will invariably cause trauma to a large volume of tissue contacted along the entire length of the cryogenic probe used to bring the probe tip to its destination.
One interesting development that addresses the issue of treating a considerably larger volume of tissue than that in proximity to the shaft of the ablation needle is described in Schaefer (U.S. Pat. No. 7,025,767), which relates to a tumor ablation needle for use to treat ablated tumors with RF energy. The tumor ablation needle described therein comprises a needle with a spreading array of individually traversing conductive tines that are independently positioned. Specifically, the disclosure describes an ablation probe comprising: an elongated member having an exterior wall, a proximal end, and a distal end; a plurality of electrical insulators extending through the elongated member, each of the insulators having a lumen, wherein the elongated member has apertures extending along the exterior wall into each of the electrical insulators; a plurality of elongated electrode tines extending through the respective insulator lumens; and a plurality of side members associated with the proximal end of the elongated member, the side members mechanically connected to the respective electrode tines through the respective apertures for being operable to independently move the respective electrode tines to extend beyond, or retract within, the distal end of the elongated member.
There are some US patents teaching designs of cryosurgical probes or catheters with variable shapes of their distal tips. These include Yon (U.S. Pat. No. 7,001,378), Maguire (U.S. Pat. No. 6,954,977), Nohilly (U.S. Pat. No. 6,951,569), Lehmann (U.S. Pat. No. 6,942,659), Mihalik (U.S. Pat. No. 6,913,604), and Isoda (U.S. Pat. No. 6,995,493). Such patents can be divided into three categories:                1. Cryocatheters with inflatable cryotips.        2. Cryoprobes or cryocatheters with tubular spiral-wise cryotips.        3. Cryoprobes with linearly extending cryotips.        
Vancelette (US Publication No. 20050177147) describes a cryoablation system which includes an elongated tubular cannula having a proximal end, a distal end, and a longitudinal axis, an expandable balloon extending from the distal end of the cannula and fluidly connected to a source of heat transfer fluid by at least one fluid path, a pump for circulating the heat transfer fluid into and out of the balloon, a probe handle coupled to the proximal end of the cannula and in fluidic communication with the balloon through the cannula, and a heat exchanger for varying the temperature of the heat transfer fluid, wherein the heat exchanger is fluidly connected to a secondary refrigerant source. The balloon is preferably expandable in response to an addition of a volume of heat transfer fluid. The heat exchanger may be positioned within the probe handle so that the secondary refrigerant can cool the heat transfer fluid to a treatment temperature before the heat transfer fluid is provided to the balloon, or the heat exchanger may alternatively be positioned within the console of the system so that the secondary refrigerant can cool the heat transfer fluid to a treatment temperature before the fluid is provided to the probe handle, or the heat exchanger may alternatively be positioned within the cannula so that the secondary refrigerant can cool the heat transfer fluid to a treatment temperature before the heat transfer fluid is provided to the balloon. In another alternative, the heat exchanger is positioned at least partially within the balloon.